We Will Protect You
by sherasan
Summary: When hoards of demons begin attacking Hogwarts, Dumbledore calls on the only people he knows who can help - Shadowhunters. Upon agreeing to help the wizards, the Clave sends a group of young Shadowhunters to help protect the school, but little do they know that the school's demon issues are worse than they thought, as they work to discover who in Hogwarts working against them.
1. Chapter 1

_A/N_

 _Hey guys, this is my first ever fanfiction I've posted online! It's basically set after the events of both of the series, though there are a few obvious things which I have disregarded – for example Dumbledore still being alive and Simon still being a vampire (spoiler alert for anyone who doesn't know already, oops). Anyway, I hope you enjoy, pleeeeaaassseeeee leave a review cause it makes me feel good (unless it's a bad review, haha)_

 _Sorry for the fact that this chapter is quite short but I needed an introduction, haha._

 _Obviously none of the characters or settings or anything like that belong to moi, instead they belong to the wonderful J.K Rowling and the fabulous Cassandra Clare._

 _\- Sherasan_

* * *

Minerva McGonagall hadn't thought she'd ever see the day when Hogwarts School of Witchcraft and Wizardry wouldn't be returning for another school year. Yet there she was, seated in the office of Albus Dumbledore, discussing how exactly they were going to cancel the return of the students after the summer only one week from the beginning of the new term.

She might have thought she was merely having a nightmare had it not been for the blood coating her robes and the four ragged gashes which sliced across her left forearm, throbbing with a searing pain as she pressed a cold towel against them tightly to stem the flow of blood. Madame Pomfrey would have a heart attack when she saw the mess she had gotten herself into.

"Have you sent the letters away to the families yet, Albus?" She asked the headmaster through gritted teeth, wincing against the pain.

Albus Dumbledore, who was seated across from her and sporting a few of his own injuries, shook his head gravely, "Not quite," He replied with his usual calm demeanour, despite the bloody claw marks raked along the left side of his face, "They are to be dispatched within the next hour, the Ministry tells me, however. The families will know by tomorrow."

Minerva nodded sadly. She couldn't bear to see the misery in her oldest friend's eyes, their azure blue usually sparkling with laughter and life, now darkened and sad. Though it hurt dreadfully, she reached her left hand out across the desk towards him, and he took hers gently in his, offering her a weak smile.

"We'll find a way to defeat these demons, Albus. I promise." She whispered, giving his hand a soft squeeze, though there was no note of hope in her voice, only defeat. For the first time in a long, long while, Hogwarts was giving up.

The attacks had begun four weeks ago, first arousing the attention of both the Hogwarts staff and the Ministry when several of the house elves recruited in the school during the summer had been found dead, their bodies strewn through the halls, mangled and dismembered beyond recognition. Immediately, a band of magical creatures specialists had been called in, for the feral teeth and claws which had obviously torn the house elves apart were of no wizards doing. Of course, no one, not even the specialists, had ever seen anything like the monster lurking through the halls of Hogwarts, and no one could be prepared for the destruction and bloodshed it caused.

The monster was extremely invulnerable to magic – even the very worst of the Unforgivable Curses appeared to merely weaken and wound the creature, and it was only when after days and days and dozens of marauders and ministry officials that they had managed to defeat it.

Then another had appeared.

And another.

And another.

Until the most recent, which both Minerva and Albus, thoroughly exhausted yet their passion and love for the halls of Hogwarts driving them onwards, had managed to assist in the defeat of today. Judging by the patterns of the others, however, they would only have a week or so, maybe even less, before the next one appeared and hungry for blood.

Hogwarts had officially been named by the Ministry of Magic itself as being in a state of dire emergency.

For a few moments, there was silence. The two friends sat there together, their hands linked across the table, as they spent what would probably be their last moments in the place they loved most, their home. The Ministry had demanded that they evacuate a long while ago, and though they had refused, Minerva knew it was finally time to depart and leave this crisis in the hands of the Ministry, for fear of their own lives.

And then, all of a sudden, something in Albus's face shifted. Slowly, he glanced up, and she saw it, that familiar, mischievous glint sparkling in his eyes. She could practically see an idea forming before he even had to say a word.

She opened her mouth to protest, to convince him that they'd done all they could and that it was time for them to leave before anything else happened, but Albus spoke before she could begin.

"Demons, did you say, Minerva?" He asked, his voice filled with a curious glee that only he could muster.

"Yes, Albus, that is what I said, but –"

"I believe I have an idea of exactly what these creatures are, Minerva," He said, and a smile broke across his features, the first smile of his she had seen in a whole month. Albus stood up, tucked his beard neatly into his belt and strode across his office towards the window sill. Immediately, an owl fluttered through, and Albus quickly scribbled down a note before tying it to the bird's leg, muttering unintelligible instructions, "And," He continued, turning around and moving towards the doorway, "I know just the people we can call on to help. An old friend of mine owes me a favour."

And with that, he was out of the door, leaving Minerva sitting at his desk, her mouth agape. The last thing she heard before the door creaked to a close was Albus's voice ringing throughout the halls.

"CANCEL THE LETTERS HOME! HOGWARTS IS NOT GOING DOWN WITHOUT A FIGHT!"


	2. Chapter 2

_A/N_

 _Hey guys, chapter two! As you will see there are quite a few changes I have made to suit my story, for example Alec's mom doesn't know that he's gay or that he's dating Magnus etc just in case anyone is confused. PLEEEEAAASSSEEEE leave a review cause it means the world! (Wow I sound really desperate haha)_

 _Anways, enjoy!_

 _Obviously none of the characters or settings or anything like that belong to moi, instead they belong to the wonderful J.K Rowling and the fabulous Cassandra Clare._

 _Sherasan, out 3_

* * *

"What the hell is going on? I'm supposed to be training right now!" Jace demanded, sauntering into Mayrse's office with a scowl etched across his face.

Clary shot him a warning glare – her boyfriend had been in a bad mood all day for the angel only knew what reason. He shook his head with a low growl, but didn't make any more complaints as he strode towards her and sat down on the arm chair beside her. Isabelle lounged on the couch across from them, her booted feet propped up on a pile of cushions, while Alec was leant against the fireplace, silent and brooding as always as he examined his nails. None of them had any idea why they had been called in by their mother for an 'extremely important' meeting.

Mayrse stood before her desk in the centre of the room, looking like the very definition of fierce with her piercing blue gaze and her elegantly muscled arms folded over her chest. Clary couldn't help but be intrigued by the woman, and knew where Isabelle had inherited her toughness and strength. This was a woman who was not to be meddled with.

"Be quiet, Jace," Mayrse snapped, and Clary felt Jace jolt slightly in surprise beside her, "This meeting is very serious and of the utmost importance, and I am certainly not in the mood to contend with your incessant complaining."

Clary hadn't thought she'd ever see Jace stunned into silence. But there he was, a look of utter shock on his face as he stared at his adoptive mother, her expression cool yet somehow feral as she glared back at him.

Whatever was going on here, it was far worse than any of them had expected.

"I have received word from the Clave concerning the four of you," Mayrse began, her heels clacking on the dark wood floors as she paced, "As you all know, when many young Shadowhunters come of age, they travel to train at foreign institutes. Now that all of you are over seventeen, should you choose to accept, the Clave have assigned you a… mission, of sorts."

It was fair to say Clary had absolutely no idea what was going to come out of Mayrse's mouth next. She'd known for a while now that she and the others would be travelling soon to explore the world of Shadowhunters outside of New York, but this seemed… different, somehow. Nudging Jace, she leaned over and whispered into his ear, "Do you have any idea what this is about?"

Jace shook his head, turning towards Mayrse as she continued.

"Following recent events concerning demons at an institution in Europe, the Clave would like to send not only the four of you but several other young Shadowhunters in training to spend a year there controlling the problem and protecting the inhabitants of the Institution."

Isabelle barked a laugh, "The Clave is sending teenagers over to fight an onslaught of demons? Are they crazy?"

"It's a minor issue, nothing a group of you cannot handle, and it will be excellent training." Mayrse replied, though there was something about her voice, and the expression of doubt on her face that told Clary she wasn't too keen on the thought of this expedition.

"And where exactly would we be staying?" Jace questioned, his face alight with what Clary could only describe as fiendish glee at the thought of an adventure like this.

"The institution is located in Britain."

"Institution?" Clary frowned, "What kind of institution?"

Mayrse sighed, massaging her temples with her fingers, "It's a school. A very special sort of school, actually. They've been having issues with demons you see, demons they have no idea how to combat, which have been appearing in the school all summer. The headmaster of the school is an old friend of one of the Downworlders who is very high up in the Clave, and he asked if he could have a group of Shadowhunters sent through to help with the problem and to protect the students attending the school if necessary."

A school? Of all the places they could have been sent, this was the last thing she had expected.

"Hogwarts School of Witchcraft and Wizardry," Mayrse picked up a document stamped with the Clave's symbol and read aloud the information written on it, "Your job will be to simply patrol the school grounds and destroy any demons who may arise within them."

Clary supposed it made sense. If the Shadowhunters had their own academy, why couldn't wizards and witches? Though she'd never encountered a witch nor a wizard before in her life, she'd read what little information the Codex had about them. They were a different sort of magical being than warlocks, as they mostly performed their spells with the use of a wand, and they preferred to keep to themselves.

"Well, I say we go," Jace announced, jumping up from the couch, "It'll be fun, right? It has always been my dream to babysit a bunch of snobby British brats."

Clary rolled her eyes. The others were grinning – Isabelle's face lit up in a way that told Clary she was already planning what hot leather outfits she was going to wear to impress the senior students, and even Alec looked excited as he strode over to his mother's desk and grabbed the Clave's document to read as much as he could about the school.

This was the adventure they had all been waiting for, yet Clary couldn't help the feeling of trepidation creeping into her mind like a warning.

"Oh, and one more thing," Mayrse added, just as they were leaving the room after Mayrse filled them in on the fine details, including that they'd be taking a portal to Britain next week just as the new school year for the students of Hogwarts began, "As well as the four of you and the other Shadowhunters, the Downworlder I mentioned earlier who was in contact with the Headmaster of Hogwarts will also be joining you."

"Who is it?" Alec asked, glancing up from his reading.

Before Mayrse could answer, a mischievously gleeful, utterly unmistakeable voice floated over from the doorway,

"That would be me, darling!" The one and only Magnus Bane announced, sashaying into the room with a smirk only he could muster, "Albus and I go way back, and he seems quite keen for me to use my expertise to teach a thing or two to his students."

"Oh. My. God." Was all Isabelle said as she left the room.

Alec's face flushed a vibrant shade of scarlet (for his mother still did not know that he and Magnus were dating) and shuffled out after his sister.

Clary and Jace followed suit, leaving Mayrse and Magnus alone to discuss the arrangements for the following week. As they walked down the hallway towards the training room, Clary glanced up at her boyfriend and said, "I've got a bad feeling about this, Jace."

"So do I," Jace replied gleefully, "And I can't wait."


End file.
